Manipulator for external bone fixation devices

ABSTRACT

A manipulator for reducing a bone fracture has adjustable elements for manipulating external fixation devices which are connected to the bone segments on either side of the fracture. The manipulator includes a circular sector having a first half sector portion and a second half sector portion. The sector portions are coupled for relative sliding movement therebetween for extending and retracting the arc of said circular sector. The manipulator includes a locking element for locking the first and second half sector portion at selected relative positions. Each of said first and second half sector portions has a generally cylindrical recess formed at the outer end thereof. 
     A pair of cylindrical bushings having an outer cylindrical surface with teeth extending parallel to a longitudinal axis of the bushings are provided. One of the cylindrical bushings are rotatably mounted in each of the generally cylindrical recesses in the first and second half sector portions. Each of the cylindrical bushings are coupled to the respective external fixation device via a shaft extending from the bushing in a direction perpendicular to the longitudinal axis thereof. 
     A drive element engages the longitudinally extending teeth on each of the bushings for rotating the bushing so that the angle of the shaft with respect to the half sector portions can be varied.

FIELD OF THE INVENTION Description of the Prior Art

External bone fixation for the therapy of skeletal fractures of limbshas been in use for many years in traumatologic medicine.

External fixation substitutes the use of immobilizing plasteringapparatuses which always involve a long rehabilitation, and, at the sametime, often avoids an operation in open air.

However, it is often a difficulty using a manipulator for performingreduction to obtain an optimum anatomic reconstruction of the fracturedskeletal segment.

The various commercially available external fixator systems do not allowsuch fracture manipulation, or they allow them only partially. Theirplacement therefor risks often making the already obtained reductionresult worse, and often with a complicated and approximative mechanicalstructure. Manipulators available are not suitable to be applied to anyexternal fixing system and can not be removed from the system, afterhaving performed the necessary fracture reduction manoeuvers.

Movements allowed with currently used manipulators do not necessarilyconcern the fracture section and require action on more than one key.

SUMMARY OF THE INVENTION

It is an object of the present structure industrial invention to suggesta means that makes the reduction manoeuvers easier by allowingmicrometric (small) displacements of the bone fragments to be reduced.

It is an additional object of the invention to allow the reductionmanoeuvers to be practised independently of each other, so as not tocompromise the already obtained fracture reduction result.

The manipulator of the present invention is intended to be removed or toremain applied to a limb through the proper fixation elements, and tothis end it is provided with clamping members that ensure a stablemaintenance of the position reached during reduction. Furthermore, itsgeometrical construction allows all monuvements to take place in thefracture section.

The present invention is realized by a manipulator which allows, byacting upon proper screw handlebar grips, a micrometric displacement ofthe fractured bone fragments in all the possible directions realizingall the degrees of freedom and all the required relative axial andangular rotations.

BRIEF DESCRIPTION OF THE DRAWINGS

The manipulator shown in a preferred embodiment thereof is given as amatter of example and not of limitation in the annexed drawings.

FIG. 1 is an axonometric front side view that shows it in the stage ofits utilization applied to a fixer of a known type;

FIG. 2 is a top isometric view the manipulation of angular rotation inthe horizontal plane made possible by the manipulator of the presentinvention;

FIG. 3 illustrates the particular mating between the toothed sector andthe endless screw that allows some rotation manoeuvers;

FIG. 4 shows in a rear isometric view the possible maneuver for theaxial slide of the fragments;

FIG. 5 represents the manipulator in a rear isometric view that showsthe manoeuver for the transverse slide in the horizontal plane; and

FIG. 6 is a front view of the detail of the sector that allows the axialrotation of the fragments.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the figures, the manipulator is made up of a sectorthat extends a quarter of a circle and is comprised of two half sectorportions 1 and 2 having guides fit for sliding angularly on each other.A screw 3 that is located in a slit 4 which goes through a large part ofsector 2 is loosened to allow the relative sliding movement of portions1 and 2.

In this way the sector arc can be varied from about 60° to about 120°.

A screw 5 engages with teeth 6 which are provided on a portion of thecontact faces of the two sectors 1 and 2 and allows a micrometricdisplacement of one sector portion with respect to the other.

Each sector portion at the end which is not slidably engaged projectsrespectively into or is formed integral with blocks 7 and 8. Blocks 7and 8 are shaped having a recess to receive bushings 9 and 10. Bushing 9and 10 are displaced by the screws 11 and 12 and have along a portion oftheir cylindrical surface teeth 13 that respectively engage the teeth ofscrews 14 and 15. The teeth of screws 14 and 15 are slightly angled withrespect to the orthogonal axis of the screw itself, as shown in FIG. 3.

From bushings 9 and 10 stems 16 and 17 project, which by means of asuitable coupling system end at and are connected to, the clamps of thefixators 18 and 19. On the stem 16 a slid coupling, 20 is provided whichconnects it to the slide bar 21 or some other axial slide system.

Such a structure may be realized through a slide bar a known externalfixation device or, will be able to be realized with any other slidesystem that acts along the longitudinal axis of the bar of the bar ofthe manipulator.

The recesses in blocks 7 and 8 include moderately elastic and transversescrews 22 and 23 fit to tighten them in order to clamp the motion of theinternal bushings 9 and 10;

From what has been illustrated it is apparent that by acting upon thedescribed screws the following displacements of the bony fragments 24and 25 connected to the relevant clamps of the external fixation devicecan be performed:

a) by acting upon the screw 26 of the device or other known axial slidesystem one determines the approaching or the removal of the fragmentsalong the longitudinal axis;

b) by acting upon the screw 12 one determines the transverse translationin the vertical plane of the fragment 24 with respect to the fragment25:

c) by acting upon the screw 11 one determines the transverse translationin the horizontal plane of the fragment 25 with respect to the fragment24;

d) by acting upon the screws 14 and 15 one adjusts the relative angle ofthe fragments in the vertical and horizontal plane;

e) Finally by acting upon the screw 5, one determines the angulardisplacement of the two half-sectors 1 and 2 and thus the rotation ofthe fragments about their own axis.

The geometric characteristics that are required in the design of thefixator are: the coplanarity of the longitudinal axes of 11 and 12 andthe convergence of these axes into the fracture focus.

When the fracture has been reduced, the screws 3 and the screws 22 and23 are tightened, so as to clamp the manipulator in its final position.In this position it can remain applied to the limb for possiblesubsequent adjusting manoeuvers. This is made possible by its reducedsize and by its extremely restricted weight.

It is however also possible to remove it by clamping the fixatorelements 18 and 19 with a simple connector of a known type.

The light weight and smallest encumbrance characteristics are aconsequence of the solutions adopted for the realization of all themovements that occur according to the suggested invention with anextremely compact instrument.

Formal and structural variations can be made to the invention withoutdeparting from the scope of the invention, which is defined by thefollowing claims.

I claim:
 1. A manipulator for reducing a bone fracture by manipulatingexternal fixation devices connected to the bone segments on either sideof the fracture, the manipulator comprising:a circular sector definingan arc having a first half sector portion and a second half sectorportion, said portions coupled for relative sliding movementtherebetween for extending and retracting the arc of said circularsector and including a locking element for locking the first and secondhalf sector portion at selected relative positions, each of said firstand second half sector portions having a generally cylindrical recessformed at an outer end thereof; a pair of cylindrical bushings having anouter cylindrical surface with teeth extending parallel to alongitudinal axis of said bushings, one of said cylindrical bushingsrotatably mounted in each of said generally cylindrical recesses in saidfirst and second half sector portions, each of said cylindrical bushingshaving a shaft extending from said bushing in a direction perpendicularto said longitudinal axis of said bushings for coupling to therespective external fixation device; and a drive element for engagingsaid longitudinally extending teeth on each of said bushings forrotating said bushing so that the angle of said shaft with respect tosaid half sector portions can be varied.
 2. The manipulator of claim 1wherein said drive element is a screw extending in a directionperpendicular to said longitudinal axis of said bushings and havingteeth thereon for engaging said longitudinal teeth on said bushings. 3.The manipulator of claim 1 wherein said arc of said circular sector maybe extended or retracted to form an arc of between 60° and 120°.
 4. Themanipulator as set forth in claim 1 wherein said longitudinal axis ofsaid bushing is coaxial with a longitudinal axis of said recess and saidaxes of the recess in said first and second half sector portions lie inthe same plane and converge on the fracture site.
 5. The manipulator ofclaim 4 wherein an adjustment element acts between said cylindricalbushings and said recesses to provide movement therebetween along saidlongitudinal axes.
 6. The manipulator of claim 5 wherein said adjustmentelement is a screw captured by each half sector portion and operativelyengaging each bushing.
 7. The manipulator of claim 6 wherein said firstand second half sector portions are coupled for sliding engagement alongcontact faces which may be displaced from one another by a screwextending perpendicular to said arc of said circular sector.